Windows slows down after a few hours!!!

[Erinvenus]

I’m having a weird issue with my Windows PC and I can’t really figure out what’s going on. After I start it up, everything runs fine for the first couple of hours. But then it slowly starts getting laggy, apps take longer to open, switching tabs feels delayed, even simple things like opening folders become sluggish.

What’s strange is that Task Manager doesn’t show anything maxed out. CPU and RAM look normal, nothing obvious eating resources. I’ve already done a virus scan (came back clean), disabled most startup programs, and made sure Windows is up to date.
Restarting the PC fixes it… but only temporarily, then it comes back again later.
Not sure if this could be some background process, driver issue, or maybe something with Windows itself. Has anyone run into something similar?